1. Field of the Invention
The present invention relates generally to a cylindrical vibration-damping device adapted for use as a suspension bushing that connects a suspension and a vehicle body, for example, and more particularly to a cylindrical vibration-damping device of fluid-filled type, which utilizes vibration damping effects based on the flow action of a fluid filling the interior.
2. Description of the Related Art
Conventionally, as one type of cylindrical vibration-damping devices applied for automotive suspension bushings or the like, there is known a fluid-filled cylindrical vibration-damping device which utilizes vibration damping effects on the basis of the flow action of the fluid filling the interior. This fluid-filled cylindrical vibration-damping device includes: an inner shaft member; an outer cylindrical member externally fitted onto the inner shaft member; a main rubber elastic body elastically connecting the inner shaft member and the outer cylindrical member, and having a plurality of pocket portions that open onto the outer peripheral face of the main rubber elastic body; a plurality of fluid chambers defined by covering the pocket portions with the outer cylindrical member and filled with a non-compressible fluid; and an orifice passage interconnecting the fluid chambers. Such a fluid-filled cylindrical vibration-damping device is disclosed in Japanese Unexamined Patent Publication No. JP-A-5-280580, for example.
In some cases, the fluid-filled cylindrical vibration-damping device employs an orifice member disposed to the inner peripheral side of the outer cylindrical member for providing the orifice passage. This orifice member extends a prescribed length in the circumferential direction while straddling the fluid chambers. Moreover, the orifice member has an orifice forming groove that opens onto the outer peripheral face thereof. The orifice passage is formed by covering the opening of the orifice forming groove with the outer cylindrical member.
Also, the fluid-filled cylindrical vibration-damping device sometimes employs a stopper mechanism for limiting relative displacement of the inner shaft member and the outer cylindrical member in the axis-perpendicular direction with the aim of improving durability of the main rubber elastic body or the like. The stopper mechanism is adapted to limit relative displacement of the inner shaft member and the outer cylindrical member by means of contact therebetween.
However, if the stopper mechanism is provided to the structure in which the orifice member is disposed to the inner peripheral side of the outer cylindrical member, the inner shaft member will strike the orifice member. Consequently, this may cause the problem that the orifice member is damaged especially in the formation zone of the orifice forming groove where a gap (the orifice passage) is formed between the orifice member and the inner peripheral face of the outer cylindrical member.
On the other hand, as disclosed in JP-A-5-280580, if a structure is employed in which the contact force between the inner shaft member and the outer cylindrical member will not exert on the orifice member, it is necessary to provide means such as further employing an intermediate sleeve between the inner shaft member and the outer cylindrical member for protecting the orifice member or the like. This may cause problems such as an increased number of components, an increased weight in association therewith, and complicated construction.